Turbine engines typically include multiple stages, each stage including a plurality of buckets. The buckets often vary in size between the stages, with some buckets, such as the last stage buckets (LSB) in a steam turbine, having a length of about 40 inches. Recently, to increase steam turbine performance, there has been a desire to increase the length of the last stage buckets to 54 inches or more.
However, with the increasing size of the last stage buckets, prototype delivery presents a manufacturing challenge involving unprecedentedly large forging dies and processes exceeding current capability. Additionally, the increasing size can extend the manufacturing cycle up to several weeks per part, while changes or modifications after the investment is made can significantly increase costs. These cost increases can often be prohibitive to making such design changes or modifications. For at least these reasons, the last stage bucket is one of the most expensive and difficult components to produce in steam turbines.
One method of reducing prototyping costs includes additive manufacturing. However, current additive manufacturing methods are limited to relatively small components. For example, three-dimensional printing, which builds up the bulk of a component from metallic powders, would take a prohibitively long time to form a large workpiece such as a last stage bucket. Other methods, which rely on deposition of molten metal or filler, would similarly take a prohibitively long time to form a large workpiece. In addition, current additive methods often include systems with structural limitations which would prohibit the formation of large workpieces.
A process and an article that show one or more improvements in comparison to the prior art would be desirable in the art.